I have been in China long enough maybe to pass on some information to prospective teachers about getting involved with a position in China. Here are a few important ones.

1) Recruitment Agencies - I would suggest not working with these people at all if possible. Try to contact schools directly as most of them do have people who are proficient in speaking English. Usually the foreign director has a sound knowledge or will usually get an English teacher to communicate with you. Recruitment agencies only want commission and they know schools are in high demand of teachers, and will throw teachers to them like sheep to the lions (although I hear some are okay). A lot of times the recruitment agencies will place false information on ads, and you won't know about it until you arrive in China already vulnerable. Go through the schools!

2) Rushing to sign a contract - You have to use your common sense on this one but if a school seems a little too much in a hurry to have you sign a contract before letting you settle in and have a nice tour of the school/city, beware! This shows the school's desperation, and it usually suggests problems with foreigners in the past. If you have a bad feeling, tell them you want some time to look around and such before signing. They will reluctantly, let you do so.

3) Beware the private/training schools - I am not saying these are all bad but more than not these are the guys to look out for. They have more freedom to be deceptive than public schools, and usually trying to trick foreigners into long work hours, and strange accommodations. Some of them don't even have a permit to hire foreigners, and will try to continuously provide you a tourist or business visa, this is illegal. Your chances are safer with a public school or at least a well established private international school.

4) Write things down - If there are issues, I have noticed long discussions seem to go no where and the next discussion just starts all over again with seemingly no recollection of any agreement prior.
Chinese directors seem to forget things on purpose, or just can't remember. Write your agreements down, ask them to look at it (since most can at least read English) and ask them if this is what you both agreed to. Write down the date, and try to have a witness present if possible. Also if you have problems, don't only tell them orally, write the problems down and give it to them. They always seem to want formal paperwork when you want something, but when they want something... it doesn't seem to matter. So make sure it works both ways.

I hope this helps, if I had known some of this earlier it would have helped me quite a lot.
Thanks.

Robert A. Kerr